When packaging a library with Vite@v6, the built code loses the named exports

[condorheroblog]

Describe the bug

I use Vite@v6 to package [email protected] to output IIFE format code. The code built in Vite@v5 contains named exports, but these named exports are lost with Vite@v6, leaving only a default export.

Here are the links to reproduce in v5 and v6:

1. https://stackblitz.com/edit/stackblitz-starters-qsvdae?file=index.js
2. https://stackblitz.com/edit/stackblitz-starters-3lubdz?file=index.js

The output above is just a different version of Vite. Using the same code, it is as follows

import { createRequire } from 'node:module';
import { build } from 'vite';

const require = createRequire(import.meta.url);

export async function buildPackage() {
  // Call the build function with build configurations
  const result = await build({
    // Do not use a configuration file
    configFile: false,
    build: {
      // Do not output files
      write: false,
      lib: {
        // Entry file is the specified package path
        entry: require.resolve('path-to-regexp'),
        // Convert package name to camel case
        name: 'pathToRegexp',
        // Output format is iife
        formats: ['iife'],
        // Output file name is the same as the package name
        fileName: 'path-to-regexp',
      },
      rollupOptions: {
        output: {
          // Export method is named export
          exports: 'named',
          // Allow extension of existing global variables
          extend: true,
        },
      },
      // Do not minify
      minify: false,
    },
  });

  // Check if result is an array, if so, take the first element, otherwise use result directly
  const _result = Array.isArray(result) ? result[0] : result;

  // If the _result does not have an output property, return
  if (!('output' in _result)) {
    return;
  }

  return _result.output[0].code;
}

console.log(await buildPackage());

console.log(`Hello Node.js v${process.versions.node}!`);

Reproduction

https://stackblitz.com/edit/stackblitz-starters-qsvdae?file=index.js

Steps to reproduce

Please npm run build

System Info

-

Used Package Manager

npm

Logs

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it's a Vue SFC related bug, it should likely be reported to vuejs/core instead.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[sapphi-red]

It seems rollup/plugins#1639 is affecting this. By setting commonjsOptions.strictRequires: 'auto', the other exports are declared in the output.

It seems the change is expected but the document only mentions about ESM output.
rollup/plugins@8f02987#diff-8d9594ca9d2280f57b2af5725720f6b0f76eabf4b137fe80d3da13d02c6f78fd

[sapphi-red]

The README doesn't say about IIFE, but it seems output.exports: 'default' works as well.

When bundling to CommonJS, i.e output.format === 'cjs', make sure that you do not set output.exports to 'named'. The default value of 'auto' will usually work, but you can also set it explicitly to 'default'. That makes sure that Rollup assigns the default export that was generated for your CommonJS entry point to module.exports, and semantics do not change.